Transport aircraft that are particularly designed for STOL (Short Take-Off and Landing) operations share certain landing gear characteristics because, by their very nature, short runways often have an unprepared surface, are uneven or sloping and have poor facilities for the loading and unloading of the aircraft. Rotorcraft (VTOL—Vertical Take-Off and Landing) operators face even more severe constraints regarding the landing area terrain. The conditions of use of the landing gear establish the design criteria, namely, rugged construction with landing loads being transferred to the primary aircraft structure, wheels of large diameter with generous tire sections not operating at high pressure and large energy absorption to retard the aircraft's potentially high descent rates.
In terms of aircraft utility, however, another requirement applies which relates to the loading and unloading of cargo or vehicles which have dimensions that closely match the door and unloading ramp opening sizes. The pitch angle of the aircraft, the roll angle and height above the local ground surface is preferably adjusted to maximize the headroom height above the loading ramp, or, alternatively, to reduce the ramp angle for vehicle movements in and out of the cargo bay.
A recurring problem in the manipulation of aircraft attitude on the ground (often referred to as the “kneeling” function) is that the systems are typically hydraulic, and that hydraulic power and its controls are heavy, expensive, and have imperfect reliability. The same is true for the retraction and extension of the landing gear. More recently, designers and operators of new aircraft are now favoring all-electric systems for reasons of ease of control, multiple redundancy, fail-operational characteristics and much improved power to weight ratio.
However, while certain advantages are readily achieved using electric attitude control, landing gear using such control, and especially landing gear for STOL and VTOL aircraft has not been appreciated. Therefore, there is still a need for improved landing gear using electric attitude control for STOL and VTOL aircraft.